hdu 1824 2-sat问题（判断）

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/*题意：u,v,w队长，队员，队长留下两个队员可以回家，两个队员留下，队长回家2-sat问题，把两个队员看成一个整体就变成一个简单2-sat问题了*/#include<stdio.h>#include<string.h>#include<algorithm>#include<stdlib.h>using namespace std;#define N  6100#define NN 5100struct node {int u,v,w,next;}bian[NN*8];int head[N],yong,low[N],dfn[N],belong[N],ans,top,index,stac[N],vis[N];void init(){    memset(head,-1,sizeof(head));    yong=index=ans=top=0;    memset(vis,0,sizeof(vis));    memset(dfn,0,sizeof(dfn));}void addedge(int u,int v){    bian[yong].v=v;    bian[yong].next=head[u];    head[u]=yong++;}void tarjan(int u){    low[u]=dfn[u]=++index;    stac[++top]=u;    vis[u]=1;    int i;    for(i=head[u]; i!=-1; i=bian[i].next)    {        int v=bian[i].v;        if(!dfn[v])        {            tarjan(v);            low[u]=min(low[u],low[v]);        }        else if(vis[v])            low[u]=min(low[u],dfn[v]);    }    if(low[u]==dfn[u])    {        ans++;        int t;        do        {            t=stac[top--];            belong[t]=ans;            vis[t]=0;        }        while(t!=u);    }}int slove(int n){    int i;    for(i=0; i<=n; i++)        if(!dfn[i])            tarjan(i);    // printf("%d\n",ans);    for(i=0; i<=n; i+=2)        if(belong[i]==belong[i+1])            return 0;    return 1;}int indx[N];int main() {    int n,m,i,u,len,v,w;    while(scanf("%d%d",&n,&m)!=EOF) {        init();        len=-1;        for(i=0;i<n;i++)  {            scanf("%d%d%d",&u,&v,&w);           indx[u]=++len;           indx[v]=++len;           indx[w]=len;        }        for(i=0;i<m;i++) {            scanf("%d%d",&u,&v);            addedge(indx[u],indx[v]^1);            addedge(indx[v],indx[u]^1);        }        if(!slove(len))            printf("no\n");        else            printf("yes\n");    }return 0;}
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